1. Field of the Invention
The present invention relates to an adjusting device for a pneumatic drive, particularly a pneumatic drive of a medical or dental instrument, for example, a handpiece or angle piece, which delivers its energy by vibration and in which the vibrations are produced by a pneumatic drive.
2. Description of the Related Art
In the past, pneumatically driven vibration systems have been offered by only two companies who own the corresponding patents. The manufacturers of instruments obtain these systems from the two companies and, until recently, mounted them exclusively in so-called scalers which are devices for removing tartar.
In the year 1992, it was recognized that it is possible by means of such vibrating tools with appropriately configured tool surfaces (covered with diamond chips, etc.) to also remove teeth or bones or other hard materials. This was disclosed in DEG 92 17 943.6 U1.
A further development of this concept is disclosed in WO96/14024A. A shaping tool is placed on such a conventional scaler with produces in a tooth a negative shape of the tool. The removal of the material is effected by the oscillations of the shaping tool and, thus, the size of the removed area is essentially larger than the tool by an extent which corresponds to this oscillation amplitude. Since the oscillation amplitude is extremely small, recesses are formed which are dimensionally very accurate, which may be defined by sharp edges and which significantly deviate from the round cross-section.
These types of recesses in a tooth are required for prefabricated tooth replacement materials which are standardized with respect to shape, such as inlays. The replacement materials have at the appropriate locations precisely formed and shaped projections which fit into the recesses produced in the above-described manner and are glued or cemented into the recesses.
Other applications relate to the root canal treatment and the cleaning of the tooth surface with oscillating brushes. For carrying out these treatments, it is also possible to use instruments which have a pneumatic drive. Of course, air flows for other apparatus and devices also require a control, usually within wide limits; however, the control still has to be sensitive.
It has now been found that the material removal capacities and the oscillation amplitudes vary substantially in one and the same instrument in dependence on the tool placed on the drive. We have found that the reason for this is the fact that the oscillation behavior of the tool, the tool shaft and the pneumatic vibration drive forms a complicated oscillation system and the maximum material removal capacity and dimensional accuracy of the formed recess in various tools or applications are due to the respectively different air flows to the pneumatic vibration drive.
Therefore, the present invention relates to an adjusting device for a pneumatic vibration drive in a dental or medical instrument of the above-described type.
An adjusting device of this type is used in practice and is composed of an adjusting sleeve arranged on the handpiece, wherein a rotation of the adjusting sleeve causes a Teflon block to close the drive air line to a different extent. This control is extremely inaccurate and not linear.
A later adjusting device by the same manufacturer, wherein the configuration thereof is unknown, includes an adjusting sleeve which can be rotated by approximately four full rotations relative to the center axis of the handpiece for moving the sleeve between the position fully closed and the position fully open. However, this adjusting device is completely useless for the purpose of the present invention because the physician using the adjusting device cannot determine the present position of the adjusting device; this determination cannot even be made when the instrument is idling in the air because the oscillation behavior of the above-described oscillating system in the unloaded state differs significantly or may differ from the behavior in the loaded state and even an experienced user cannot find any indication concerning the adjustment of the adjusting device.
Moreover, the device known in the art is in spite of a large adjusting distance entirely incapable of exhibiting an even approximate linear behavior, so that there are adjusting ranges in which even a small rotation of the adjusting sleeve results in a substantial change of the air flow, while in another range even a substantial rotation of the adjusting sleeve produces only a slight change of the air flowing through.